Abstract

Cold expansion is widely used to improve the fatigue life of fastener holes. However, fatigue crack often initiates at the entrance edge of the hole due to lower compressive or tensile residual stress as a result of cold expansion. In the current study, the entrance edge of the cold expanded hole has been ultrasonically impacted with a specially designed pin, and comparative fatigue tests are performed to evaluate the influence of the ultrasonic impact treatment on the fatigue performance of the cold expanded holes. The findings show that the ultrasonic impact treatment imparted a larger compressive residual stress and created a fillet arc at the entrance edge, which resulted in an obvious reduction in the fatigue crack propagation rate in the earlier stage of the fatigue crack growth and extended the fatigue life of the cold expanded holes further.

中文翻译：

---

超声冲击处理对冷膨胀AA6061-T6孔疲劳性能的影响

摘要

冷膨胀被广泛用于改善紧固件孔的疲劳寿命。然而，由于冷膨胀的结果，较低的压缩或拉伸残余应力会在孔的入口边缘处引发疲劳裂纹。在当前的研究中，冷膨胀孔的入口边缘已通过特殊设计的销钉进行了超声波冲击，并进行了比较疲劳试验，以评估超声冲击处理对冷膨胀孔疲劳性能的影响。研究结果表明，超声冲击处理会赋予较大的压缩残余应力，并在入射边缘产生圆角弧，